1. Field of the Invention
This invention relates to an exhaust gas purification apparatus in a combustion engine, including a hydrocarbon adsorbent and a catalytic converter.
2. Description of the Related Art
As discussed in Japanese Patent Application Laid-open No. 95/144,119, in order to purify hydrocarbons discharged from a combustion engine, a three-way catalytic converter and an integrated catalytic converter, which is an integration of a hydrocarbon adsorbent and a three-way catalyst, are disposed in an exhaust passage of the combustion engine so that the three-way catalytic converter and the integrated catalytic converter are arranged adjacent to each other in series at a location under a floor-panel of a vehicle.
Also, in order to purify hydrocarbons, Japanese Patent Application Laid-open No. 95/174,017 discloses a pre-three-way catalytic converter provided in an exhaust manifold, and a three-way catalytic converter and an integrated catalytic converter provided in an exhaust passage which is connected to downstream the exhaust manifold. Similar to the foregoing related art, the three-way catalytic converter and the integrated catalytic converter are arranged adjacent to each other in series at a location under a floor-panel of a vehicle.
With such an exhaust gas purification apparatus, the hydrocarbon adsorbent in the integrated catalytic converter is generally capable of adsorbing hydrocarbons at a lower temperature such as during the start-up period of the combustion engine. Therefore, hydrocarbons discharged from the combustion engine are adsorbed in the integrated catalytic converter when a three-way catalyst employed therein has not been activated.
Now, a desorbing temperature of the hydrocarbon adsorbent is generally lower than an activation temperature of the three-way catalyst. Thus, during the period after reaching to the desorbing temperature until the activation temperature is reached, there may be a possibility that a part of the hydrocarbons desorbed from the hydrocarbon adsorbent can be discharged into the atmosphere without being oxidized with the three-way catalyst.
On the other hand, the hydrocarbon adsorbent naturally desorbs hydrocarbons at a stretch when a temperature of the hydrocarbon adsorbent has exceeded the desorbing temperature. Consequently, an air-fuel ratio at the hydrocarbon adsorbent shifts to the rich side, and the three-way catalyst cannot oxidize hydrocarbons effectively because the three-way catalyst fulfills its function under a certain air fuel ratio, that is, the stoichometric ratio. Thus, there is also a possibility even after activation of the three-way catalyst that a part of the hydrocarbons desorbed from the hydrocarbon adsorbent can be discharged into the atmosphere without being oxidized.
It was therefore an object of this invention to provide an exhaust gas purification apparatus in a combustion engine which can decrease the amount of hydrocarbons discharged to the atmosphere without oxidizing the three-way catalyst or oxidize catalytic.
In order to achieve the above object as well as other objects, this invention provides an exhaust gas purification apparatus in a combustion engine comprising an exhaust manifold of an engine, a hydrocarbon adsorbent that adsorbs hydrocarbon at a lower temperature, and that desorbs hydrocarbon at a higher temperature. The adsorbent is disposed in the exhaust manifold, and a catalytic converter that purifies hydrocarbon is also disposed in the exhaust manifold at a position upstream from the adsorbent. Further the catalytic converter and the hydrocarbon adsorbent are arranged adjacent to each other in series.
These and other objects and many of the attendant advantages of this invention will be readily appreciated as the same become better understood by reference to the following detailed description when considered in connection with the accompanying drawing.